This probably won't be very helpful but...
I have some Godzilla manga collections that i picked up in Manhattan some time in the late 1990's. I think one is manga of '54/'84 and the other is adaptations some of some of the 60's & 70's films.
I got them at a Japanese book store about a block from Grand Central Station. Unfortunately I'm not sure of the name or address of the place. (There was a place that sold Dim Sum across the street...)